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Unfortunately, losing the ability to detect the subtle social clues that help you know when you’re being doused with sarcasm or even dissed with a big fat lie may actually be an early warning sign of dementia, according to a new study by researchers at the University of California, San Francisco.

The scientists, who reported their findings at a recent meeting of the American Academy of Neurology, have discovered that a certain type of neurodegenerative disease may chip away at the ability to understand the social, physical and verbal cues that help people recognize indirect language, such as sarcasm, and even deceit.

“These are the patients who fall for all the online scams, and lose all their money, because they just don’t get the lie,” said lead author Katherine Rankin, a neuropsychologist in the UCSF Memory and Aging Center, who led the new study. “They don’t understand sarcasm. They would think 'The Colbert Report' is real.”

Rankin and her team focused on a a specific type of neurodegenerative disease called frontotemporal dementia, or FTD, a group of disorders in which patients can experience behavioral symptoms such as personality changes, a loss of inhibition and social tact as well as language difficulties, such as an inability to understand words. They found that the disorder appears to increase gullibility as well.

To compound the problem, FTD is often misdiagnosed as depression or even a severe midlife crisis, Rankin said. Though it’s tough to get an accurate estimate, the UCSF scientists estimate that FTD is the most common dementia diagnosed in patients under the age of 60, and as common as Alzheimer’s disease among patients age 45 to 64.

In the study, Rankin and her colleagues made use of The Awareness of Social Inference Test, or TASIT, which uses videotaped subtle-as-a-sledgehammer scenarios of people lying or being sarcastic.

People were asked simple yes or no questions about what they saw. TASIT scores were then matched to maps of brain structure to see whether the specific brain regions that deteriorated due to the disorder could be linked to extreme gullibility.

If it proved true, the scientists reasoned, the inability to understand sarcasm and recognize lies could then provide another diagnostic clue to help doctors spot FTD.

The UCSF study included 175 participants, 103 people with various dementias, including all forms of FTD, and a control group of 72 healthy older adults, who showed no signs of neurological problems.

Healthy subjects easily spotted sarcasm
The healthy individuals could easily identify the lies and sarcasm. Patients with Alzheimer’s disease also could quickly recognize lies, though the sarcastic scenarios were harder for them to detect. However, patients with FTD couldn’t recognize either the sarcastic scenarios or the lies.

Brain imaging studies showed that the left lateral orbitofrontal cortex, a part of the brain associated with predicting punishment, was involved in patients’ inability to understand deceit. The finding suggests the basic fear of doing something wrong, like lying, stays intact in most dementias, but gets lost in FTD, even in its initial stages, said Rankin.

Interpreting the type of sarcasm used in this study — which was more complex than simply hearing the annoyed voice of a teen sighing "duh" — required large parts of both temporal lobes, including brain areas that help a person understand emotions and social concepts, like what “sarcasm” actually is.

“Brain and behavior correlation is very important, especially the brain areas affected by this disorder,” said Dr. Alan Lerner, director of the Memory and Cognition Center at University Hospitals Case Medical Center in Cleveland. “This is important work because it can help us identify patients earlier. Too many are missed.”

Indeed, Rankin hopes that medical professionals will start to look at the inability to recognize lies and sarcasm as an FTD symptom, rather than a peculiarity of aging.

Currently, FTD treatment is focused on symptom management and lifestyle changes. But clinical trials focused on new disease-modifying medications look promising, said Rankin.

“Right now, identifying the problem early and seeing the right specialist can really help the patient and family learn how to cope,” she said. “Our ability to understand lies and sarcasm, well, those are basic things that help us connect with other people, and when that’s lost, it can be devastating."